Baroness Manningham-Buller was the Director of the UK's MI5 security service from 2002 to 2007. She was already a counter-terrorism expert by the time of the Lockerbie bombing in 1988 and went on to rise up through the organisation. Earlier this year, she gave a series of lectures to the BBC.
You can listen to her lecture on terrorism here .
In it, she looks at the lasting effects of the 9/11 attacks and analyses what kind of crime they constituted. The lecture also includes details of her role in the discussions involving international security agencies in the days following 9/11.
Link to the BBC website : http://www.bbc.co.uk/podcasts/series/reith